Webmaster in a Nutshell, Third Edition

Name

<?...?>

Synopsis

A processing instruction allows developers to place attributes specific to an outside application within the document. Processing instructions always begin with the characters <? and end with the characters ?>. For example:

<?works document="hello.doc" data="hello.wks"?>

You can create your own processing instructions if the XML application processing the document is aware of what the data means and acts accordingly.

<?target attribute1="value"
attribute2="value" 
... ?>